Pressure transducers of the type which comprise a thin, relatively flexible diaphragm portion of suitable material, such as silicon or ceramic, on which either a selected resistive element or a capacitive plate is printed whereby exposure to a fluid pressure source causes deflection of the diaphragm will cause a change in the resistive value of the resistive element or a change in the spacing of the capacitive plate with a mating capacitive plate and concomitantly a change in capacitance are well known in the art.
When used as a low pressure sensor, economical packaging of the transducer in a housing so that an effective seal is obtained while at the same time preventing stress related to the mounting and sealing of the transducer from influencing the output becomes problematic. This is caused, at least in part, by the significant difference in thermal expansion between the material used to form the transducer, e.g., silicon, ceramic or the like, and the housing of plastic or the like. A conventional sealing arrangement involves placement of a ring of sealing material around an inlet pressure port in a housing and mounting the transducer so that the pressure sensitive diaphragm is precisely aligned with the pressure port. This conventional arrangement not only involves stress isolation issues, it also limits flexibility in design choices in defining the location of the transducer within the package.
Another problem involved with liquid pressure transducer designs whether for use in monitoring high or low fluid pressure sources relates to their use in environments, such as automotive, industrial and communication, which contain electromagnetic radiation which cause interference (EMI) with the transducer signal. Typically, an outer electrically conductive metallic housing electrically tied to ground is used in which to mount the transducer package in order to shield the assembly from such EMI. This approach, however, not only adds to the expense of the product by adding to the part count of the assembly but it is also cumbersome and adds to the physical size of the package which is undesirable since such transducers are typically located in areas in which space is at a premium.